The present invention relates to a method for fluid inlet temperature monitoring for centralized heat disinfection of dialysis machine inlet lines supplied by a central water processing system. The present invention also relates to a dialysis system for centralized heat disinfection of dialysis machine inlet lines that includes fluid inlet temperature sensors at the fluid inlet lines of dialysis machines on a loop which is supplied from a central water processing system with heated water.
Renal dysfunction or failure and, in particular, end-stage renal disease, can cause the body to lose the ability to remove water and minerals and excrete harmful metabolites, maintain acid-base balance and control electrolyte and mineral concentrations within physiological ranges. Toxic uremic waste metabolites, including urea, creatinine, and uric acid, can accumulate in the body's tissues which can result in serious adverse health consequences if the filtration function of the kidney is not replaced. Dialysis is commonly used to replace kidney function by removing these waste toxins and excess water. In one type of dialysis treatment—hemodialysis—toxins are filtered from a patient's blood externally in a hemodialysis machine. Blood passes from the patient through a dialyzer separated by a semi-permeable membrane from a large volume of supplied dialysis solution. The waste and toxins dialyze out of the blood through the semi-permeable membrane into the dialysis solution, which then can be suitably processed if reused or discarded.
Hemodialysis treatments are typically conducted at a clinic since the hemodialysis machines generally can require a continuous water source, reverse osmosis machinery, and drain lines for discarding the large volumes of water and dialysis solution used during a single treatment. Dialysis clinics also can provide dialysis treatment for multiple out-patients or in-patients at the same location. The dialysis machines can be supervised and maintained on-site by a trained clinical staff in a convenient and efficient manner. Dialysis machines need periodic cleaning and disinfection to maximize the efficiency and minimize bacterial and other microorganism levels within the system. Cleaning and disinfection can be done periodically (e.g., daily), or as needed after a long power down or after a completion of a dialysis treatment and before reuse of the same machine. Cleaning and disinfection, for example, can be done on a machine between the dialysis treatments of different patients that are received on the same machine. Disinfection may be chemical or heat based. Disinfectants are usually used in liquid form in order to be passed through the hydraulic system of the machine and discharged from the machine using a drain line. Even if a machine is routinely chemically disinfected, the manufacturer still may recommend periodic heat disinfections of the machine. This hydraulic system often includes one or more of water treatment, dialysate preparation, and extracorporeal dialysis modules, and other fluid pathways in the machine that will be reused. Heated water has been generated locally at the individual machines for heat disinfection. For example, in some hot water disinfection programs, heated water at a predetermined temperature is generated at the individual machines using an internal heater and the heated water is circulated through the hydraulic system of the dialysis machine for a predetermined amount of time, such as a circulation of water at 80° C. for one hour, or other suitable temperatures and times.
Some fluid heating and heat disinfection programs found in the patent literature for dialysis machines, for example, are directed towards closed loop systems that measure internal device temperatures locally at the machine. U.S. Pat. No. 4,894,164 (Polaschegg, Fresenius AG) shows an apparatus for treating blood in an extracorporeal circuit which has water from a supply water introduced into a dialysis solution container equipped with an electrically operated heater and associated temperature sensor, and also includes temperature sensors disposed in the arterial and venous blood paths inside the machine, wherein the temperature sensors report to a temperature regulating unit within the machine. Polaschegg does not have details on a disinfection program. U.S. Pat. No. 5,651,893 (Kenley et al.) shows disinfection of a dialysis machine that includes determining or selecting a disinfection temperature in advance which is controlled by the operation of a water heater in the machine and strategically placed thermistors in the machine which report temperatures of the water, and the circulation time is controlled by a clock in the CPU of a control module and the operation of the pumps and valves of the machine. U.S. Patent Application Publication No. 2009/0012450 A1 (Shah et al.) shows an extended use dialysis system which includes a cassette that includes in-line heater for heating fluid within the dialysis machine for disinfecting the machine and its lines. Shah et al. shows the temperature sensors may be incorporated in one or more places to control the temperature of the sterilizing water and to insure that the lines of the machine are thoroughly heated to kill bacteria or other microorganisms remaining, and the temperature sensors may include thermocouples, thermistors, or other suitable devices for detecting temperatures and reporting temperatures to the controller of the dialysis machine. U.S. Pat. No. 7,749,393 B2 (Brugger et al.) shows a batch filtration system for preparation of sterile fluid for renal replacement therapy which includes a temperature regulator, e.g., a temperature sensor combined with logic in controller, which regulates power to the heater to ensure a required temperature is maintained and not exceeded. Brugger et al. also shows the controller may simply respond to some predefined rate of temperature rise of the temperature sensor. U.S. Pat. No. 6,153,102 (Kenley et al.) shows disinfection of dead-ended lines in medical instruments which includes a step of experimentally determining an optimal dwell time by circulating water heated to a disinfection temperature TH into a fluid line, allowing it to remain in the line for a first dwell period, measuring the temperature in the fluid line, and withdrawing the fluid from the line, and repeating the steps in a specified manner. These references do not directly address disinfection of water inlet lines which externally supply the dialysis machines, which may not be reached by any local disinfection program that may be programmed to run in the individual machine.
As indicated, hemodialysis treatments conducted at a clinic can require a continuous water source, among other elements. Development of some central water processing systems for some dialysis clinics has been undertaken. Referring to FIG. 1, for example, a dialysis system 10 for a clinic or other medical care facility which uses a central water supply system 12 for heat disinfection of fluid inlets to the machines is shown. The system 10 relies on a single temperature sensor 13 to monitor water temperature at the outlet 14 of the central water supply system 12. The outlet 14 is located where the central water supply system 12 directly feeds into a distribution circuit 15 (referred to as the “loop”), which supplies the heated water to all of the dialysis machines 16A-C on the loop 15. The heated water supplied in the loop 15 is available to the individual dialysis machines 16A-C via a respective fluid inlet 17A-C at each dialysis machine. The monitoring of the water temperature at the outlet of central water processing system is based on an assumption that such restricted temperature monitoring can reliably predict that water supplied to the fluid inlets of all of the dialysis machines on the loop, wherever located, will remain hot enough to provide adequate disinfection of all of the machine inlet lines connected to the loop.
As shown in FIG. 1, when the distribution loop containing the heated water is servicing several dialysis machines, the chances of having a temperature variation along the distribution loop is significant. Under the current method, having just a temperature monitor at the central water system where the heated water originates simply is not sufficient to adequately ensure that the temperature of the water is sufficient for the disinfection purposes. Under the current method, dialysis treatment centers or clinics must simply over-estimate and raise the central water system's temperature of the water to temperatures far in excess of what is needed for disinfection simply to ensure that the heated disinfection temperature of the water is achieved along the entire line of dialysis machines that are hooked to the distribution loop. This can result in significant energy costs. Further, there is always the risk that one or more dialysis machines are not receiving water having a high enough temperature for purposes of disinfection. Thus, under the current method, many assumptions are made or, out of an abundance of caution, significantly higher water temperatures are used to accommodate the temperature variation along the line. As explained below, with the present invention, significant energy savings can be achieved with the method and system of the present invention and, further, proper precautions are taken to ensure that each and every dialysis machine receives the proper temperature of water for purposes of disinfection.
The present investigators have recognized that temperature gradients may occur at fluid inlets to dialysis machines which are supplied with hot water for disinfection from a central distribution loop of a central water processing system, which may destabilize the disinfection operations and which cannot be reliably predicted by outlet monitoring alone at the central water processing system. The present investigators have further recognized that even if dialysis machines on a central water processing system have their own internal temperature monitoring and fluid heating capability, that the fluid inlet line temperatures from the loop also need to be monitored to ensure that water for inlet line disinfection is reliably available from the central water loop at a specified temperature or temperature range for that function.
The present investigators further have recognized a need to provide a temperature monitoring approach and configuration for a dialysis system which can enhance heat disinfection control and performance for fluid inlet lines of a central water processing system, even when the central distribution loop supports numerous dialysis machines on a relatively lengthy loop and/or one or more subloops are located in the same or different rooms, floors, buildings, or other different areas of the facility.